Pneumatic inner tube



@ct. 9, W34. A. D. ROBERTSON PNEUMATIC INNER TUBE Filed Nov. 15, 1933 Patented Oct. 9, 1934 PNEUMATIC INNER, TUBE Albert D. Robertson, Davidson County, Tenn.

Application November 15, 1933, Serial No. 698,171

2 Claims.

The purpose of my invention is to provide an inner tube so formed along its outer periphery, which comes in contact with the inner surface of the tread portion of the casing, or for a distance beyond the tread portion, that the said outer periphery portion of the inner tube will be brought into a state of compression both longitudinally and in cross-section of the inner tube upon its being inflated within a casing, thereby automatically closing or tending to close punc tures.

The invention consists in forming the outer periphery of the inner tube with transverse raised and depressed portions, the transverse depressed portions, when the inner tube is in a deflated state, having the same or approximately the same circumference as the cross-sectional circumference of the inside of the casing in which the inner tube is to be used, and the raised portions being of a greater circumference than the cross-sectional circumference of the inner surface of the casing in which the tube is to be used.

The raised and depressed portions will give the inner tube an accordion effect circumferentially thereof, which will enable the tube to be shortened circumferentially of the tread and thereby placed in a casing of a less large diameter than the diameter of the tube. Upon the tube being inflated in the casing the raised portions will be depressed inwardly and the depressed portions will assume their normal state, being in contact or approximately in contact with the inner surface of the casing.

In the accompanying drawing Fig. 1 is a detailed View of the vertical section of the inner tube in a deflated state, with dotted casing superimposed;

Fig. 2 is a cross-sectional view of the deflated tube shown along the line MN in Fig. 1;

Fig. 3 is a detailed view of the deflated inner tube showing said tube placed in a casing;

Fig. 4 is a cross-sectional view of the deflated tube along line MN of Fig. 3 placed in a casing;

Fig. 5 is a cross-sectional view of a tube with a differently formed raised cross-sectional area;

Fig. 6 shows a cross-sectional view of the tube inflated in a casing; and,

Fig. 7 is a view of a vertical section of the tube inflated in a casing.

My invention is based upon the idea of forming an inner tube as heretofore described, the body of which will give the tube the eifect of an accordion, thereby allowing the tube to be compressed while in a deflated state and placed in a casing which is less both in cross-sectional diameter and circumferential diameter than the inner tube when not compressed. Upon the tube being placed in a casing in this manner, and while still in its deflated state, the depressed areas of the tube will be pressed inwardly and cause the perimeter of said 50 depressed portions to assume a smaller circumferential length in cross-section than they would assume on the outside of the casing. Upon the tube being inflated in the casing these depressed areas would be shoved out against the inner surface of the casing, and at that time would have the same perimeter as they would have in a deflated state outside the casing. The raised areas, on the contrary, during inflation, would be held by the inner surface of the casing and would go into compression, both longitudinally of the tread and cross-sectionally of the tread, and a portion of this compression would be transmitted to the depressed areas, thereby placing the entire tread portion of the tube in compression both circurn- 7 ferentially and in cross-section.

Fig. 1 illustrates a section of a deflated tube X,

A representing the crest of a raised area and D representing one of the ends of a raised area.

B represents the crest of a depressed area. This 30 tube would be used in a casing of a size illustrated by dotted casing W, which is superimposed in the drawing of the casing. It will be noted that the line KK, which represents the inner surface of the tread portion of the casing W, is in contact with or approximately in contact with the depressed areas B.

Fig. 2 is a cross-sectional view of Fig. 1 on line MN and shows the inner tube X in deflated state with a dotted casing superimposed. It will be 9 noted that the depressed area represented by the arc CBD is practically the same as the dotted arc CBD representing the inner surface of the tread portion of the casing, and the raised area represented by the arc CAD is a greater length than the dotted arc CBD.

Fig. 3 shows a longitudinal view of section of the inner tube X placed in casing W. It will be noted that the raised areas A and A in Fig. 3 have been brought a little closer together by reason of the tube having been confined in the casing W, and also that the crests of the raised areas are now in contact with line KK, which represents the inner surface of the tread portion of the casing W, and the depressed areas B have been forced inwardly and away from the l tread portion of the casing W.

Fig. 4 is a cross-sectional View of the inner tube X and casing W along line MN in Fig. 3. Here again it is to be noted that the raised area represented by the arc CAD is now in contact with the inner surface of the tread portion of the casing W, and the depressed area represented by the line CED has been forced inwardly and away from the tread portion of the casing.

Figs. 1, 2, 3 and 4 represent inner tubes with the raised areas consisting of arcs, which begin in the side walls of the casing and gradually increase until they reach the maximum depth at the center of the tread portion of the tube.

Fig. 5 illustrates a cross-section of the tube X with a raised area of a different formation from the are illustrated in the above four figures.

Fig. 6 is a cross-sectional view of the inner tube X inflated in a casing W, and Fig. 7 is a longitudinal view of inner tube X inflated in a casing W.

I do not confine myself alone to the shapes, sizes and spacings of the raised areas illustrated in the drawing attached. The heights of the raised areas and the lengths of the raised areas and the number of degrees covered on the crosssectional circumference of the inner tube, and the shape of raised areas and the distance of the raised areas apart, will have to be determined by the manufacturer in order to get the amount of compression desired for various types of tubes.

As stated beicre, the basis of my invention is:

That the depressed portion CED, as shown in Fig. 2, in its deflated state and before being place" in a casing, is practically the same circumferential length in cross-section as the inner surface of the casing illustrated by dotted lines CB3 in Fig. 2, and that the raised areas, represented by are CAD in Fig. 2, is of a greater circumferential length than the inner surface oi the casing represented by dotted line CBD, when said tube is in a deflated state and before being placed in the casing. That when the tube is placed in the easing the raised areas will come closer together, as shown in Fig. 3, which will enable the tube to seat in the casing, and at this time the raised reas, represented by are CAD in Fig. 4, will be lying against the inner surface of the casing as shown in Fig. 4, and the depressed areas, represented by are CS1) in Fig. 4, will have been contracted and forced inwardly away from the inner surface of the casing. ihe arc CED in Fig. 4, representing a depressed area, is apparently stretched upon the tube being inflated in the easing W so as to assume the position shown in Fig. 6. This is not the case, for the depressed area represented by the arc CBD in Fig. 4 really returns to its normal position upon the tube being inflated in casing W as shown in Fig. 6. On the other hand, the raised area represented by arc CAD in Fig. i is really put in compression, both in cross-section and longitudinally of the tread,

upon the tube being inflated in casing W as shown in Figs. 6 and 7, so that the tread portion of the tube, and as far down the sides as desired, according to the design of the raised portions, will be put in compression both circumferentially and longitudinally of the tread, and as a result punctures made in the compressed area will be automatically closed or close to such an extent as to allow the tube to be serviceable for a considerable while after the object causing the puncture has been removed.

Having described my invention, what I claim as new and desire to secure by Letters Patent is:

1. An inner tube, comprising a body having the ti ead portion of comparatively thick rubber, the tread portion being made up of raised and depressed portions arranged transversely of the tread portion, the are cutting the tops of said raised portions, when the tube is deflated and outside the casing, being of a greater length than the circumferential length of the inner surface of the tire casing in which the tube will be used, and the circumference of the tube along crosssections cutting the depressed portions being of a length equal to or approximately equal to the length of the perimeter of the inner surface of the casing cross-section in which the tube is to be used, and cross-sections cutting the raised portions being of a length greater than the length or" the perimeter of the inner surface of the casing in crosssection in which the tube is to be used.

2. An inner tube for pneumatic tires comprising an endless tubular member of elastic material, the outer periphery or tread portion of which 13 depressions lying transverse of the tread throughout the tread portion, the contour of the depressed portions, when the tube is in a deflated condition, approximately corresponding with the contour and length of the inner surface of the casing in cross-section in which the tube is to be used, and cross-sectional contour of the raised portions, when the tube is in a deflated condition, being of greater length than an are traced on the inner surface of the tread portion of the casing subtending the same number of degrees as are subtended by the raised portions in cross-section, so that the raised portions will be forced inwardly toward the cross-sectional center of the tube and become compressed both longitudinally and in cross-section upon the tube being inflated in a casing, and a portion of this compression will flow into the depressed portions of the tube, thereby bringing the entire tread of the tube in compression, both in cross-section and circumferentially.

ALBERT D. ROBERTSON.

ade up of alternating raised portions and 

